San Antonio Mayor Julian Castro, left, and brother Joaquin Castro stand at the podium during preparations for the Democratic National Convention at Time Warner Cable Arena on September 2, 2012 in Charlotte, North Carolina. The DNC that will start on September 4 and run through September 7, will nominate U.S. President Barack Obama as the Democratic presidential candidate. less

San Antonio Mayor Julian Castro, left, and brother Joaquin Castro stand at the podium during preparations for the Democratic National Convention at Time Warner Cable Arena on September 2, 2012 in Charlotte, ... more

Photo: Joe Raedle / Getty Images

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CHARLOTTE, NC - SEPTEMBER 02: San Antonio Mayor Julian Castro stands on stage during preparations for the Democratic National Convention at Time Warner Cable Arena on September 2, 2012 in Charlotte, North Carolina. The DNC that will start on September 4 and run through September 7, will nominate U.S. President Barack Obama as the Democratic presidential candidate. less

CHARLOTTE, NC - SEPTEMBER 02: San Antonio Mayor Julian Castro stands on stage during preparations for the Democratic National Convention at Time Warner Cable Arena on September 2, 2012 in Charlotte, North ... more

Photo: Streeter Lecka / Getty Images

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San Antonio, Texas Mayor Julian Castro talks to reporters at the Democratic National Convention in Charlotte, N.C., Tuesday, Sept. 4, 2012. The mayor will give the keynote speech at the DNC.

San Antonio, Texas Mayor Julian Castro talks to reporters at the Democratic National Convention in Charlotte, N.C., Tuesday, Sept. 4, 2012. The mayor will give the keynote speech at the DNC.

Photo: Jae C. Hong / Associated Press

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San Antonio Mayor Julian Castro, left, who will be the convention keynote speaker, and his twin brother, state Rep. Joaquin Castro, who is running for U.S. Congress, are interviewed at the Democratic National Convention in Charlotte, N.C., Monday, Sept. 3, 2012. less

San Antonio Mayor Julian Castro, left, who will be the convention keynote speaker, and his twin brother, state Rep. Joaquin Castro, who is running for U.S. Congress, are interviewed at the Democratic National ... more

Photo: Charles Dharapak / Associated Press

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San Antonio Mayor Julian Castro, left, who will be the convention keynote speaker, and his twin brother, state Rep. Joaquin Castro, who is running for U.S. Congress, are interviewed at the Democratic National Convention in Charlotte, N.C., Monday, Sept. 3, 2012. less

San Antonio Mayor Julian Castro, left, who will be the convention keynote speaker, and his twin brother, state Rep. Joaquin Castro, who is running for U.S. Congress, are interviewed at the Democratic National ... more

Photo: Charles Dharapak / Associated Press

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Mayoral candidate Julian Castro smiles after announcing his runoff election against Phil Hardberger at his campaign headquarters in the evening on Saturday, May 7, 2005. Castro was leading the early voting with 39 percent of the votes. less

Mayoral candidate Julian Castro smiles after announcing his runoff election against Phil Hardberger at his campaign headquarters in the evening on Saturday, May 7, 2005. Castro was leading the early voting ... more

Councilman Julian Castro, center, candidate for San Antonio mayor, addresses the crowd Tuesday, June 7, 2005, in San Antonio at Castro's campaign headquarters. At left is his girlfriend, Erica Lira, and at right is his twin brother, Joaquin. Retired state judge Phil Hardberger held a narrow lead over Castro late Tuesday in the mayoral runoff. less

Councilman Julian Castro, center, candidate for San Antonio mayor, addresses the crowd Tuesday, June 7, 2005, in San Antonio at Castro's campaign headquarters. At left is his girlfriend, Erica Lira, and at ... more

Photo: BAHRAM MARK SOBHANI / AP

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San Antonio Mayor Julian Castro, left, and his brother, state Rep. Joaquin Castro give an interview during preparations for the Democratic National Convention at Time Warner Cable Arena on Sept. 3, 2012 in Charlotte, N.C. less

San Antonio Mayor Julian Castro, left, and his brother, state Rep. Joaquin Castro give an interview during preparations for the Democratic National Convention at Time Warner Cable Arena on Sept. 3, 2012 in ... more

Photo: Streeter Lecka / Getty Images

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In the eye of the camera: Julian Castro.

In the eye of the camera: Julian Castro.

Photo: Rick Dunham / Hearst Newspapers

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Mayor Castro answers reporters' questions at the Democratic National Convention.

Mayor Castro answers reporters' questions at the Democratic National Convention.

Photo: Rick Dunham / Hearst Newspapers

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Julian Castro at a Democratic National Committee session.

Julian Castro at a Democratic National Committee session.

Photo: Rick Dunham / Hearst Newspapers

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Julian Castro addresses the National Association of Latino Elected and Appointed Officials (NALEO).

Julian Castro addresses the National Association of Latino Elected and Appointed Officials (NALEO).

Photo: AP

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Julian Castro (in the blue tie) shakes hands with President Obama on July 17. The San Antonio mayor is flanked by his twin brother Joaquin.

Julian Castro (in the blue tie) shakes hands with President Obama on July 17. The San Antonio mayor is flanked by his twin brother Joaquin.

Photo: Bahram Mark Sobhani / AP

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President Obama walks from Air Force One with Texas State Rep. Joaquin Castro, his twin brother the mayor and Rep. Charlie Gonzalez, upon his arrival for a fundraising visit to San Antonio on July 17.

President Obama walks from Air Force One with Texas State Rep. Joaquin Castro, his twin brother the mayor and Rep. Charlie Gonzalez, upon his arrival for a fundraising visit to San Antonio on July 17.

Photo: Bahram Mark Sobhani / AP

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San Antonio Mayor Julian Castro gives the keynote address at the Texas Democratic Convention in Houston on June 8.

San Antonio Mayor Julian Castro gives the keynote address at the Texas Democratic Convention in Houston on June 8.

Photo: Pat Sullivan / AP

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Julian Castro easily won a second term as mayor.

Julian Castro easily won a second term as mayor.

Photo: San Antonio Express-News

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Julian Castro smiles as an audience applauds him.

Julian Castro smiles as an audience applauds him.

Photo: San Antonio Express-News

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Democrats view Julian Castro as a future star of the national party.

Democrats view Julian Castro as a future star of the national party.

Photo: San Antonio Express-News

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Mayor Castro is considered one of his party's best political orators.

Mayor Castro is considered one of his party's best political orators.

Photo: San Antonio Express-News

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Joaquin Castro left, introduces his twin brother and San Antonio Mayor Julian Castro during the the 2012 Texas Democratic Party State Convention at the George R. Brown Convention Center Friday, June 8, 2012, in Houston. less

Joaquin Castro left, introduces his twin brother and San Antonio Mayor Julian Castro during the the 2012 Texas Democratic Party State Convention at the George R. Brown Convention Center Friday, June 8, 2012, ... more

Photo: James Nielsen / Chronicle

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Democratic Congressional Candidate Joaquin Castro speaks prior to introducing his twin brother and San Antonio Mayor Julian Castro during the the 2012 Texas Democratic Party State Convention at the George R. Brown Convention Center Friday, June 8, 2012, in Houston. less

Democratic Congressional Candidate Joaquin Castro speaks prior to introducing his twin brother and San Antonio Mayor Julian Castro during the the 2012 Texas Democratic Party State Convention at the George R. ... more

The national fight for the hearts and votes of Latino voters is being shaped by two young Texans with Hispanic roots.

In the past week, San Antonio Mayor Julian Castro and Republican Senate nominee Ted Cruz both energized their parties’ national conventions with impassioned stories of the family’s immigrant experience and only-in-America success.

But despite their similar tales of faith and triumph, the liberal Democrat from South Texas and the conservative Republican from Houston expressed starkly different views of the role of government in protecting personal freedom and building economic success.

Cruz, 41, speaking to the Republican National Convention in Tampa, described his life as “an American love story” — the love of freedom, including freedom from intrusive government.

Castro, 37, the first Latino keynote speaker in the history of the Democratic Party, spoke of a different lesson from his family’s immigrant experience. To Castro, government should help Americans fulfill their own American dreams.

“The dream is universal, but America makes it possible,” Castro told an enthusiastic crowd at a packed sports arena in Charlotte. “And our investment in opportunity makes it a reality.”

Cruz’s speech last week and Castro’s address Tuesday night reflect the political battle being waged by both parties not only for the votes of Latinos — the fastest-growing bloc of voters in the nation — but for control of the political mystique engendered by the American Dream.

“Horatio Alger lives, over and over, at both party conventions,” said University of Virginia government professor Larry J. Sabato.

The twin national television debuts also gave America a preview of the boundless political potential of two Texans groomed by their parties for future greatness.

“Watching Castro and Cruz is like watching a high school all-star game,” said Dan Schnur, director of Jesse M. Unruh Institute of Politics at the University of Southern California. “We’re going to be watching these players competing in higher levels through many, many years.”

The dueling speeches by the young Texas rising stars reflected the efforts by both parties to place a Latino voice behind the party’s traditional messages of liberalism and conservatism. But presidential scholars say that a few headline speakers is not a substitute for a policy agenda that is relevant to the population.

“I don’t think either political party has quite figured out how to quite appeal to Latinos,” said Scott McLean, professor of political science at Quinnipiac University. “Both are experimenting with having different kinds of speakers at the podium. That kind of appeal is really very limited. The parties have to show they’re working on behalf of Latinos.”

For Texas voters, however, the emergence of Castro and Cruz could remake the face of state politics for the next generation. Cruz, who defeated establishment favorite David Dewhurst in the July 31 Republican runoff, is a heavy favorite to become the first Latino senator in Texas history. And Democrats predict that Castro’s nationally televised moment will catapult him to statewide prominence.

Reveling in Castro’s prominence, Texas Democratic Party Chairman Gilberto Hinojosa said the San Antonio mayor “represents everything the Democratic Party is going through in America, a party that understands that this is a land of opportunity for everyone.”

“We need to elect a statewide leader. I believe Julian Castro is the person to do that,” Hinojosa said. “He’s dynamic. He’s got a great story: single mom to Harvard law school.”

Great family story or not, Castro faces an uphill battle for statewide office in Texas, the most Republican big state in the nation, one that hasn’t elected a Democrat to statewide office in this century. In his speech Tuesday, Castro melded the individualism revered by conservatives with the compassion of liberals.

“In Texas, we believe in the rugged individual,” he told Democrats in Charlotte. “Texas may be the one place where people actually still have bootstraps, and we expect folks to pull themselves up by them. But we also recognize there are some things we can’t do alone. We have to come together and invest in opportunity today for prosperity tomorrow.”

Valerie Martinez-Ebers, a University of North Texas political science professor, said Democrats need Castro’s speech to pay dividends in 2012, while Republicans are more concerned about the long term.

“In the Democratic Party, Latinos are very important to that base,” said Valerie Martinez-Ebers, a University of North Texas political science professor. “They need to be important to Republicans but they’re not (yet). They’re just a token.”

“Both parties understand that Latino voters represent the nation’s demographic future and they’re going to grow as a percentage of the electorate,” said Schnur, a longtime Republican strategist. “The fight for their support is only going to get more intense.”

Also contributing to this report were Summer Ballentine and Emily Wilkins.